A throw-away rotating tool is a tool in which a cutting head having cutting edges is detachably held on a body. In the related art, a throw-away rotating tool is known in which a cutting head has a projecting portion (projecting coupling portion) whose diameter increases toward the rear end side, and a tool shank (body) has a recessed portion whose diameter decreases toward the distal end side see FIGS. 1, 8 and etc. in JP-T No. 2002-501441). The throw-away rotating tool disclosed in JP-T No. 2002-501441 is configured such that after the projecting coupling portion is inserted into the recessed portion in a state with the body and the cutting head shifted in phase around the axis, the cutting head is relatively rotated around the axis, thereby bringing the projecting coupling portion and the recessed portion into engagement with each other by making use of elastic deformation of the recessed portion of the body.